I think it's awesome that your boy loves music.... years ago I offered my son a pair of PSB M2 and told him I'd buy him a nice Integrated Amp and CD player. He held his phone up and said "no thanks, my music is all in here...."
I almost cried, anyway hopefully you can show him all about NAS storage and or music files and he doesn't have a phone yet so ...
My vote would be for a Bluesound power node and a cheap tablet.